1. Field of the Invention
The present invention relates in general to an internal combustion engine, and more particularly to a fuel supply system of an internal combustion engine for an outboard motor.
2. Description of Related Art
Outboard motors are increasingly employing fuel injection systems. Fuel injected engines offer such advantages as improved fuel economy, lower emissions, increased engine power, and better fuel distribution into each engine cylinder.
A conventional fuel injection system typically includes a vapor separator to remove vapor from the fuel supply. The vapor separator typically includes a fuel bowl or tank that is arranged within the cowling of the outboard motor. A float or similar level controller controls the fuel level within the tank. A high pressure pump often delivers fuel from the vapor separator to a fuel rail which in turn feeds the fuel to the fuel injectors. The fuel injectors inject a specific fuel volume into the engine during each combustion cycle. Excess fuel from the fuel rail is returned to the vapor separator.
Some fuel vaporizes within the fuel supply system due to heat and to pressure drops within the circulation loop between the vapor separator and the fuel rail. The vapor separator thus often includes a vapor discharge port to vent fuel vapors from the fuel tank. The fuel vapors are usually introduced into engine to be burnt with the normal fuel-air charge. Prior venting mechanisms, however, have been overly complicated, employing check valves which open only when the vapor pressure exceeds a predetermined value.